I can’t recall if this was specifically mentioned in the books, but when did the incestous relationship of Cersei and Jaime start? I wonder if it was before she met Rhaegar as we know she was infatuated with him. Do you think it could have started after Aerys rejected Tywin’s offer, out of bitterness? If it started before they met, would she have kept both relationships going if she married Rhaegar, or would she have ditched Jaime?

I’d consider joannalannister to be the real authority on this, but I’ll give it a try.

Some level of sexual exploration started really young. They got caught by Joanna, and she had them separated, and Joanna died when they were 7, three years before the Tourney where the Rhaegar thing was brought up. It certainly continued until they were 12 and Cersei was brought to court, after which there was a three year period in which Jaime and Cersei didn’t really see each other much. Then Jaime becomes a Kingsguard, Tywin takes her back to Casterly Rock, and they don’t really see each other for another three years.

Then Cersei comes back to King’s Landing as Robert’s bride and the two of them are together for fifteen years.